Psoralens as photoactive probes of nucleic acid structure and function: organic chemistry, photochemistry, and biochemistry.

PERSPECTIVES AND UMMARY .............................................................. 1152 INTRODUCTION ..................................................................................... 1155 ORGANIC AND STRUCTURAL CHEMISTRY OF PSORALEN AND ITS ADDUCTS ................................................................... 1158 Naturally Occurring Psoralens ................................................................. 1158 Synthesis and Radiolabeling of Psoralens .................................................... 1158 Monofunctional Psoralens ....................................................................... 1160 Relative Reactivity of Different Psoralens with Nucleic Acids ............................ 1161 Psoralen Monoadducts and Diadducts Formed With DNA and RNA .................... 1162 PHOTOCHEMICAL PROPERTIES OFPSORALENS ........................................ 1165 Spectroscopic Properties of Psoralen Molecules ............................................ 1166 Reactive States for Monoadduct and Crosslink Formation in Polynucleotides ........ 1170 Controlled Production of Monoadducts and Diadducts in DoubleStranded Nucleic Acids ............................................................. 1172 THE USE OF PSORALENS AS PROBES FOR NUCLEIC ACID STRUCTURE AND FUNCTION ..................................................... 1172 Chromatin Structure .............................................................................. 1172 Cruciforms ......................................................................................... 1175 Torsional Tension ................................................................................. 1176 Secondary Structure in Single-Stranded Nucleic Acid ...................................... 1177 Stabilization of Nucleic Acid Complexes ...................................................... 1184 FUTURE DIRECTIONS ............................................................................. 1186